Of course, you can remove all machines from the domain and then shut down the domain controller.
Without a domain controller, all machines will only use their local users. If you're sharing files you'll have to either enter credentials for the share or keep all user names and password synced on all machines. Also, group and machine policies will be local ...
You may set the login- and lock-screen images by:
Run Settings > Personalization > Lock screen
Set the Background drop-down to "Slideshow"
Click "Add a folder"
Navigate to the folder and click OK to select.
It's not uncommon to have one drive fail in a RAID5 and then have a second drive fail on rebuild - if you haven't taken care of the array.
The core of the problem is that some unused data blocks may slowly degrade (bit rot). It simply isn't detected (and automatically repaired/remapped by the drive) because it's not been read back. However, on a rebuild all ...
iSCSI might still do the job in your case. For Windows, try Starwind VSAN which has a free version and can export your disk over iSCSI to another machine. The only thing, you do not need to create a virtual disk but just export a physical drive. Here's a guide: https://www.starwindsoftware.com/help/PhysicalHardDrives.html